Answer:
Her marriage angered her brother Henry IV who denied her the right to the crown of Castille and willed it to his daughter Joanna.
Explanation:
Isabella I who was the half-sister to Henry IV was betrothed in marriage to Ferdinand II of Aragorn at a very tender age. However, when Henry fell out with John II of Navarre, the father of Ferdinand, he decided to marry off his sister to another Prince. This led to a long series of deliberations and changes in the men who were being considered for marriage with Isabella.
At the age of 18, Isabella made the decision to marry Ferdinand even though they were First cousins. They married secretly even obtaining fake approval from the Pope. After this, they eloped. On finding out about the marriage, Henry IV was enraged and withdrew from Isabella, the right to the Crown of Castille, and gave it to his daughter Joanna. When he died five years later, Isabella returned to the Kingdom to claim her right to the crown.
